Kiwi - it's pretty straight-forward... just stand in the water, about where the little wavelets are breaking, and zoom in on a swell. Follow it in, constantly refocusing on it, just making sure to pan with the wave, keeping the camera aimed at the same part the whole time. Right when it's about to break, trip the shutter, while continuing to pan. Ideally, you'll have a long enough shutter speed to not stop the action (though that would be interesting in its own right). With luck, you get something like this... Without luck, you get something like most of the 80 photos I took standing in the ocean yesterday afternoon...